[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 0/6] xen,xend,tools: NUMA support for Xen
* Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx> [2006-07-11 16:28]: > > > What sort of box are these numbers taken from? If it's not a NUMA > > > system then the slowdowns are rather poor. We're particularly > > > interested in not slowing down non-NUMA and small-NUMA (e.g., AMD > K8) > > > x86 systems. They are what we really want to see measurements from. > > > > The measurements are taken from a two-way Operton 248 (2.1Ghz) , > > small-NUMA. I agree that there is significant overhead, however, we > > aren't talking about fast path here; correct me if I'm wrong. We > > are only adding overhead to during domain startup. The end result > > being we pay for local memory allocation at creation time while > > benefiting from local memory access for the lifetime of the domain. > > > > I'm going to gather some oprofile data to see if I missed something > > obvious, but in general I think that having local memory is of greater > > benefit for the lifetime of a domain than the cost we incur during its > > creation. > > What do the numbers look like on a 1 node system? For K8 small numa, I don't have a 1 node system available. > > The shadow mode code potentially churns the page allocator a fair bit. > It'll be disappointing if we have to add complexity of quicklists etc. Yeah, I forgot about shadow mode; good point. > > It does kind of surprise me that the overhead is as high as you've > measured. In the case where there's memory available in the favoured > node I'd expect allocation performance to be very similar. 4 times > slower and worsening for large allocations seems odd -- 0.3 microseconds > a page is a bit more than I'd expect during back-to-back allocations. > It's certainly worth trying to understand the overhead a bit more. I agree. I'm a little mystified by the overhead as well. On the larger system, ballooning up to 23G had something like 11% overhead, which was more reasonable, though the domain creation tests showed more than 11% on that system as well. I'll get the oprofile data and take a look. -- Ryan Harper Software Engineer; Linux Technology Center IBM Corp., Austin, Tx (512) 838-9253 T/L: 678-9253 ryanh@xxxxxxxxxx _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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